Railroad crossings have long been dangerous for motorists because inattention, failure to see approaching trains, or failure to correctly judge the speed of approaching trains can lead to catastrophic accidents and loss of life. Some studies have shown that the cause of two-thirds of the rail associated deaths in the United States are highway/railway crossing accidents. These studies provide evidence that thousands of people die in crossing accidents every year, with approximately fifty percent of the crossing accidents resulting in death. Many highway/railroad crossings still have only passive warning signs, but increasing numbers today have active protection and include active warning devices located an extended distance from the crossing to provide adequate warning.
Conventional warning systems typically use an electric connection across the rails of an electrically isolated section of track. A detector is wired across the tracks so that when the train enters the isolated section, the tracks form a closed circuit and the detector receives a signal to indicate the presence of a train. A controller connected to the detector by long, in-ground wires, senses the short-circuit as the presence of a train and activates the signal devices. These hard-wired connections are subject to many faults and, like any electrical connections, are subject to being shorted out by water, ice, corrosion or other problems.